1. Field of the Invention
The present invention relates to colorings. More particularly, it relates to a class of colorings that are useful as food colorings and that in that use are characterized by having substantially reduced toxicity.
2. The Prior Art
Colorings are widely used in the food industry to enhance and improve the appearance and appeal of virtually all the processed foods now marketed. There is, however, a growing concern that food colorings present health hazards. The United States Food and Drug Administration has recently restricted or banned several widely used food colorings, for example, Food, Drug and Cosmetic Red. No. 4 and FD&C Violet No. 1, as unsafe. A direct and self-evident solution to the color toxicity problem is to discover and employ colorings which, when ingested and absorbed into the body, have no ill effects. It has proved most difficult to do this and supply the wide range of colors desired by the food processing industry.
An indirect solution to the food color toxicity problem has also been proposed. It has been noted that if a food color has a molecular size which is too great to permit the color to pass through the walls (the mucosal linings) of the gastrointestinal tract, the food color will not be absorbed into the body and there is no possibility of toxicity. Conventional food colors themselves are not large enough to prevent absorption. It is thus necessary to chemically bind together a plurality of color bodies (also known as optical chromophores or optically chromophoric groups or bodies) or to chemically attach the color bodies to a molecule sufficiently large to restrict absorption. The means for chemically attaching chromophores to a large "carrier" molecule must meet certain stringent criteria. It must not interfere with the optical color properties of the chromophores. It also must not break down, i.e., hydrolyze, metabolize, or degrade, at either the conditions of food processing or the conditions of the gastrointestinal tract.